Toxicokinetics of nickel in rats after intratracheal administration of a soluble and insoluble form

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Abstract
Ni is present in the atmosphere from automotive exhaust. Workers such as welders can also be exposed to inhaled Ni. Laboratory studies (90 days) were performed to determine whole body distributon of 2 chemical forms of Ni in female Wistar rats. A single injection of 15.mu.Ci 63Ni, NiCl2 as a solution of NiO as a suspension (100 nmol), was administered intratracheally. Rats were sacrificed at post-exposure intervals of 0.5, 2 and 8 h, 1, 3, 7, 15, 30, 60 and 90 days and major organs and tissues were analyzed for 63Ni by liquid scintillation counting technique. Soluble NiCl2 was readily distributed throughout the body and rapidly cleared from the tissues. Insoluble NiO was distributed slowly to other organs from pulmonary tissues. The rate of decline of 63Ni from various organs in the case of NiO was similar to that of NiCl2, except for the lung and associated lymph nodes. After NiO administration, these organs showed a high retention of Ni after 90 days. Ni in soluble form was rapidly absorbed from the site of deposition following pulmonary exposure; Ni as NiO was retained in lungs and related lynphatics for a considerable period. The amount of Ni in other organs following NiO exposure although initially low in all tissues, declined similar to organs following NiCl2 exposure. NiO was possibly converted to a soluble form of Ni before it was translocated from lungs to other organs and low enviornmental levels of insoluble forms of Ni, which persisted in the lung and lymph nodes, had the potential for assimilation in these tissues.